Ambient light level detector including transient suppression circuitry

ABSTRACT

A circuit which includes a level detector circuit which is operated at two output levels, one level being indicative of a first ambient light condition and the second being indicative of another light condition, therebeing a timing circuit operated by the Schmitt trigger and an output circuit operated by the timing circuit after a predetermined delay to overcome transient and temporary changes in ambient light.

United States Patent 7 [151 3,665,224

Kelsey [451 May 23, 1972 [54] AMBIENT LIGHT LEVEL DETECTOR 3,175,1523/1965 Shafer ..307/31 1 v3,315,134 4/1967 $521101] ...317/148.52,879,456 3/1959 Pinckaers ..307/31 1 CIRCUITRY I 3,238,423 3/1966Giuffrida ...317/148.5 7 Inventor: Newton D. Kelsey, Houston, Tex.3,221,317 1 1/1965 Femgno ..307/31 1 73] Assignee: Arthur P. Ruth Pnrrary Examiner-Donald D. Forrer Assistant Examinerl-laro1d A. Dixon Filed!Sept. 8, Attorney mnald Gum 21 A LN 70025 1 PP 0 I i 57 ABSTRACT Acircuit which includes a level detector circuit which is [52] US. Cl..307/3ll, 307/273, 307/235, operated at two output levels one levelbeing indicative of a 307/236 250/215 first ambient light condition andthe second being indicative of [51] Int. Cl. ..H0lj 39/12 another licondition, therebeing a timing circui operated [58] Field of Search..307/273, 236, 262, 311, 235; by the s hmitt trigger and an outputcircuit operated by the 317/1485; 250/215 timing circuit after apredetermined delay to overcome transient and temporary changes inambient light.

[56] References Cited 2 Cl 1 Drawing Figure UNITED STATES PATENTS3,313,939 4/1967 Spencer .3Q7 /3 l1 H ANIMAL FEEDER 1 5+ 5+ 5+ 5+ i I 5+IO 1 i l AAAIA PATENTEDMM 23 I972 Newton D. Kelsey INVENTOR ATTORNEYAMBIENT LIGHT LEVEL DETECTOR INCLUDING TRANSIENT SUPPRESSION CIRCUITRYSUMMARY OF PROBLEM AND SOLUTION The present circuit finds use in aremotely situated animal feeder. Normally, animals expect to find foodabout the beginning of the day and the end of the day. This isparticularly true for those which are at least partially domesticated,such as flocks of birds which are fed to keep them in the vicinity of ahunting reserve or the like. The same is also true of fish feeding. At acertain time of the day, fish food will be dispensed in the water andattract a school of fish. The apparatus of the present invention isparticularly useful with a remote animal feeder. The feeder utilizedwith the present invention incorporates a storage bin for receiving asubstantial quantity of feed, a measuring device, and a dispenser. Theanimal feed is dispensed to a point outside the animal feeder. it may bebroadcast in a circle about the feeder or dumped outwardly as in thecase of a fish feeder. The food is distributed routinely and at acertain time, preferably at dawn and dusk. It should be recognized thatregularity of the feeding is quite important to the health and welfareof the animals which rely on the feeding device of the presentinvention.

In the spring of the year, the device may be installed in the vicinityof ground nesting birds such as doves or quails to feed an entire flock,including chicks. The apparatus of the present invention is intended asa control mechanism for an animal feeder which is triggered at daylightand dark. The present invention is summarized as including a sensorwhich is made responsive to the rising and setting of the sun. A lightsensitive resistor responds to the changes in ambient light level tooperate the animal feeder cooperative with the present invention. Thelight sensitive resistor is included in the circuit which is connectedwith the level detector circuit. As the input voltage to the Schmitttrigger is altered, it assumes one of its two operative outputconditions. The two conditions are determined by the light sensitiveresistor in an input voltage divider connected with the level detectorcircuit. The Schmitt trigger is connected to an output circuit whichoperates a solenoid for dispensing of the feed. In between these twocircuits is a time delay circuit. The time delay circuit provides anamount of delay in operation which is sufficient to overcome transients.Thus, should a person shine a flashlight on the sensor, no false signalis obtained unless the light is maintained on the device for an extendedperiod of time. Likewise, should the sensor be temporarily covered overduring the daytime, the device would not misread the temporary signal,treat it as dusk, and dispense the feeding which is normally intendedfor dusk. Such erratic operations are prevented through the use of thedelay circuit as will be described.

Many objects and advantages of the present invention will become morereadily apparent from a consideration of the following s'pecificationand drawings, which are:

The single drawing is a schematic wiring diagram of the light sensor ofthe present invention.

in the drawings, attention is first directed to a light sensitiveresistor 10. It is connected in series with an additional resistor 12.The two are connected between ground and a source of voltage, typicallythe B+ supply, which is provided with the equipment. The voltage drop atthe midpoint is determined by the resistance of the circuit component10. As the amount of light falling on the resistor is increased, itsresistance between terminals decreases and hence, the voltage at thejunction increases. The voltage at the junction between the tworesistors is coupled by an additional resistor 14 through a seriesresistor 16 and input to a transistor 18. The transistor 18 cooperateswith an additional transistor 20 to function as a level detectorcircuit. AC signals are grounded through the use of a grounded capacitor22 which couples high frequency signals to ground.

The level detector circuit, including the transistors 18 and 20, has anemitter resistor 24 which is grounded. The output of the transistor 20is formed across the resistor 24. A collector resistor is found at 26which is connected to ground through an additional resistor 28.Considering the level detector circuit, the output signal is formedacross the resistor 24. The signal is either high or low, dependent onwhether or not the transistor 20 is driven to saturation. It can onlyassume two values. Thus, if the transistor 20 turns on slightly, asignal is provided to the base of the transistor 18 which drives itfurther on and which thereby returns a signal 'to the base of thetransistor 20 which drives it to saturation. Hence, saturation isattained when the circuit is switched on, or the transistor 20 is turnedoff and the voltage across the resistor 24 is nearly zero.

The two levels of output signals from the level detector circuit arethus coupled to the next stage, that portion of circuitry which providesa time delay.

The output of the level detector circuit circuit is taken across theresistor 24. The output is supplied to a pair of capacitors 30 and 32.The capacitors 30 and 32 have different functions depending on whetheror not the device is operative at daylight or dark. More will be notedconcerning this hereinafter. The capacitor 32 is grounded on one side bya resistor 34 and is input to the base of a transistor 36. The

transistor 36 shares a collector resistor 38 with an additionaltransistor 40. The two transistors 36 and 40 are both grounded at theiremitters. The common collector load resistor 38 forms signals which aretransferred by a connective resistor 42 to an additional transistor 44.The transistor 44 is switched on or off by the signals supplied to theresistor 42. The transistor 44 has a collector load resistor 46. Whenthe transistor 44 is rendered conductive, a sizeable drop across theresistor 46 is formed. This drop is coupled through a capacitor 48 to anadjustable resistor 50 and series resistor 52 back to the base of thetransistor 40. A diode 54 grounds negative signals accumulated on thecapacitor 48.

The delay circuit described in detail will be described in I operationafter its connection with an output circuit are set forth.

The delay circuit has an output signal which is formed across a resistor46. The resistor 46 is connected through a fairly small base inputresistor 56 to an emitter follower transistor 58. The emitter followertransistor 58 forms a signal across its emitter resistor 60. The emitterresistor 60 develops an output signal which is supplied to a switchingtransistor 62. The switching transistor 62 handles a substantial currentflow for operation of a solenoid 64. When the transistor 62 switches onor off, an inductive voltage has formed in the solenoid 64, and for thisreason, a diode 66 is connected across the solenoid 64. The solenoid 64is mechanically connected to the animal feeder 68 for purposes ofdispensing feed. The animal feeder is shown in application Ser. No.56,923, filed July 21, 1970.

In operation, the resistor 10 is sensitive to the ambient light. It ispreferably placed in a position to be exposed to sunlight. When it isexposed to an adequate level of light, the resistance drops toward aminimal value. Upon this occurrence, the resistor 14 couples a highlevel voltage to the level detector circuit. Once a threshold voltage iscrossed, the level detector circuit forms a high level output across theresistor 24. When the input signal to the Schmitt trigger drops belowthe threshold value, a low output is formed across the resistor 24.Thus, the ambient light condition, of whatever gradation, is convertedinto a bilevel signal condition by the level detector circuit.

The signal from the level detector circuit is coupled through acapacitor 32. The capacitor 32 passes the leading edge of a positivegoing signal. For instance, this occurs at dawn when the light level onthe resistor 10 increases. Considering the advent of dawn, thetransistor 36 is switched on and conducts heavily. This forms a negativegoing signal at the collector of the transistor 36. The negative goingsignal is coupled to the transistor 44 which is switched on. Asthetransistor 44 conducts, the voltage across the resistor 46 increases.This in-' as illustrated. The transistor is switched on. After aninterval, the capacitor 48 charges up to a positive level beingdetermined by the drop across the resistor 46. When the charge becomessufficiently positive, it drives the base of the transistor 40 towardcut-off, and current flow is terminated through the transistor 40. Thiscut-off reduces current flow through the common collector resistor 38and drives the collector voltage up, thus functioning as a monostablemultivibrator and terminating the wave form which is formed by thecombination of transistors 36, 40 and 44. This wave form terminates,and, so to speak, the circuit times out. This increase in current turnson the transistor 62, which is used as an electronic switch. Thiselectronic switch connects the solenoid 64 from the positive supply toground. This thereby permits current flow through the transistor 62 andthe solenoid 64 to operate the animal feeder. lts term of operation islimited as the monostable multivibrator times out.

Timing of the monostable multivibrator is determined by the charge inthe capacitor 48 and the adjustment of the resistor 50. This timing canbe adjusted from perhaps a fraction of a second upwards to 8 or 10seconds, depending on need. It functions in the same manner for bothdaylight and dark.

The foregoing discusses operation of the apparatus at dawn. The leveldetector circuit forms a positive going signal which is connectedthrough the capacitor 32 and to the remaining portions of circuitry tocause it to function. The reverse is true at dusk. At dusk, the amountof light falling on the light sensitive resistor 10 is reduced. As thelight is reduced, its resistance is increased. This inputs a low levelsignal to the level detector circuit which responds by switching to itslower level output. As it switches down to its lower level output, thenegative going signal is coupled through the capacitor 32 to thetransistor 36. However, such signal is of no avail to the operation ofthe transistor 36 because it is already cut-off. However, the negativegoing signal is connected through the additional or parallel capacitor30 and directly to the collector of the transistor 36. This negativegoing signal simulates the same signal which is engendered through theoperation of the transistor 36. That is, at either dawn or dusk, thecollector of the transistor 36 sees a negative going signal. Hence, thetime delay circuit which includes the transistors 36, 40 and 44functions in the same manner. The only difference is that the signal atdawn is coupled through the base of the transistor 36 while the signalat dusk is connected directly to the collector of the transistor 36.Thereafter, the delay circuit functions in the same manner. The amountof delay is again determined by the cooperation of the capacitor 48, ofa selected size, and the series resistor 50. Again, the output signal ofthe time delay circuit is developed across its resistor 46. When thetransistor 44 conducts, a positive going signal is transferred to theconnective resistor 56 to the emitter follower transistor 58. This,again, switches on the solenoid 64 through the use of the switchingtransistor 62 to operate the animal feeder 68. Both daylight and duskfunction the same in the operation of the animal feeder.

Erratic light conditions are prevented from triggering the distributionof feed, such as a flash of lightening at night, through operation ofthe capacitor 22 which grounds transients at the input. Thus, a finiteinterval must pass before a change in light condition is sensed by thedevice.

While many alterations and variations of the present inven tion may beadapted, the scope of the present invention is determined by the claimswhich are appended hereto.

What is claimed is:

l. A circuit for detecting ambient light levels such as dawn and duskfor an animal feeder which comprises:

a light sensitive resistor means being incorporated in a voltage dividerconnected between two voltage levels, the midpoint thereof beingconnected with a level detector circuit forming an output signal at oneof two levels, said level detector circuit having a predeterminedthreshold level' said light sensitive resistor means being sensitive tovaria tions of ambient light to cause said level detector circuit toform an output signal which is indicative of light levels above acertain predetermined level, and the other signal indicative of lightlevels below a certain predetermined level;

said level detector circuit being connected to a monostablemultivibrator by means of a first coupling capacitor which is connectedto the base of a transistor therein, and further including a secondcapacitor connected to the collector of said transistor within saidmonostable multivibrator;

an output circuit connected with the animal feeder for causing same todistribute animal feed; and,

said monostable multivibrator being connected between said leveldetector circuit and said output circuit means for operating said outputcircuit means for a time interval which is adjustable and whichinitiates only after passage of a predetermined interval of light levelas sensed by said light sensitive resistor means.

2. A circuit for detecting ambient light levels such as dawn and duskfor an animal feeder which comprises:

a light sensitive resistor means;

a level detector circuit means incorporating said light sensitiveresistor means therein and sensitive to changes in resistance thereof asa result of variations of ambient light, said level detector circuitmeans forming two output signals across an output resistor, oneindicative of light levels above a certain predetermined level and theother indicative of light levels below a certain predetermined level;

a pair of capacitor means connected with said output resistor;

a first transistor switch means connected to one of said capacitor meansat its base;

said transistor means including a collector which is connected to thesecond capacitor means, said means further including a load resistorthrough which current is developed by said transistor means when it isswitched on and off;

additional circuit means connected to said transistor means forcontrolling the interval of time the voltage level at the collector oftransistor means is maintained at a level initiated by a signal fromsaid level detector circuit means initiated by a signal from said leveldetector circuit means coupled through one of said capacitor means;

an output circuit connected with the animal feeder for causing same todistribute animal feed; and,

said transistor means being connected to said output circuit means foroperating said output circuit means for a time interval which isadjustable and which initiates only after passage of a predeterminedinterval of light level as sensed by said light sensitive resistormeans.

1. A circuit for detecting ambient light levels such as dawn and duskfor an animal feeder which comprises: a light sensitive resistor meansbeing incorporated in a voltage divider connected between two voltagelevels, the midpoint thereof being connected with a level detectorcircuit forming an output signal at one of two levels, said leveldetector circuit having a predetermined threshold level; said lightsensitive resistor means being sensitive to variations of ambient lightto cause said level detector circuit to form an output signal which isindicative of light levels above a certain predetermined level, and theother signal indicative of light levels below a certain predeterminedlevel; said level detector circuit being connected to a monostablemultivibrator by means of a first coupling capacitor which is connectedto the base of a transistor therein, and further including a secondcapacitor connected to the collector of said transistor within saidmonostable multivibrator; an output circuit connected with the animalfeeder for causing same to distribute animal feed; and, said monostablemultivibrator being connected between said level detector circuit andsaid output circuit means for operating said output circuit means for atime interval which is adjustable and which initiates only after passageof a predetermined interval of light level as sensed by said lightsensitive resistor means.
 2. A circuit for detecting ambient lightlevels such as dawn and dusk for an animal feeder which comprises: alight sensitive resistor means; a level detector circuit meansincorporating said light sensitive resistor means therein and sensitiveto changes in resistance thereof as a result of variations of ambientlight, said level detector circuit means forming two output signalsacross an output resistor, one indicative of light levels above acertain predetermined level and the other indicative of light levelsbelow a certain predetermined level; a pair of capacitor means connectedwith said output resistor; a first transistor switch means connected toone of said capacitor means at its base; said transistor means includinga collector which is connected to the second capacitor means, said meansfurther including a load resistor through which current is developed bysaid transistor means when it is switched on and off; additional circuitmeans connected to said transistor means for controlling the interval oftime the voltage level at the collector of transistor means ismaintained at a level initiated by a signal from said level detectorcircuit means initiated by a signal from said level detector circuitmeans coupled through one of said capacitor means; an output circuitconnected with the animal feeder for causing same to distribute animalfeed; and, said transistor means being connected to said output circuitmeans for operating said output circuit means for a time interval whichis adjustable and which initiates only after passage of a predeterminedinterval of light level as sensed by said light sensitive resistormeans.